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Monday 17 July 2017

Atom- and step-economical nucleophilic arylation of azaaromatics via electrochemical oxidative cross C-C coupling reactions

 
Atom- and step-economical nucleophilic arylation of azaaromatics via electrochemical oxidative cross C-C coupling reactions
Green Chem., 2017, 19,2931-2935
DOI: 10.1039/C7GC00789B, Communication
O. N. Chupakhin, A. V. Shchepochkin, V. N. Charushin
A simple and efficient electrochemical method for the synthesis of asymmetrical bi(het)aryls through direct functionalization of the C(sp2)-H bond in azaaromatics with fragments of (hetero)aromatic nucleophiles has been developed.

Green Chemistry

Atom- and step-economical nucleophilic arylation of azaaromatics via electrochemical oxidative cross C–C coupling reactions

Abstract

The synthesis of asymmetrical bi(het)aryls through direct functionalization of the C(sp2)–H bond in azaaromatics with fragments of (hetero)aromatic nucleophiles has first been carried out under electrochemical oxidative conditions. This versatile method for C–C bond formation between two aryl fragments can be realized under very mild potential-controlled oxidative conditions, and it does require neither incorporation of any halogen atoms or other leaving groups, nor the use of metal catalysts. The use of the electrochemical SHN methodology for modification of azaaromatic compounds has first been demonstrated.
   
str1
9-(1H-Indol-3-yl)-10-methylacridinium tetrafluoroborate (3e) Red crystals, 189 mg (96%). M.p.: 192-193 °C. 1H NMR (500 MHz, [D6]DMSO): δ 12.44 (s, 1H), 8.80 (d, 2H, J=9.5 Hz), 8.43-8.39 (m, 4H), 8.14 (d, 1H, J=2.6 Hz), 7.90-7.86 (m, 2H), 7.70 (d, 1H, J=8.2 Hz), 7.32 (t, 1H, J=7.4 Hz), 7.17-7.10 (m, 2H), 4.88 (s, 3H) ppm. 13C NMR (126 MHz, [D6]DMSO): δ 156.2, 141.2, 137.9, 136.5, 131.1, 130.5, 127.9, 127.1, 125.6, 122.9, 121.2, 119.0, 118.9, 112.7, 107.9, 38.6 ppm. Elem. Anal. Calcd. For C22H17N2BF4: C 66.69, H 4.33, N 7.07 Found: C 66.78, H 4.39, N 7.10.
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Methionine sulfoxide


v
Methionine sulfoxide (2a). 1H NMR (D2O, 400 MHz): δ = 3.79 (m, 1H), 2.81-3.08 (m, 2H), 2.66 (s, 3H), 2.23 (m, 2H) ppm. The NMR data matched the data obtained for commercial methionine sulfoxide. ESI HRMS m/z C5H12O3NS [M+H]+ : calcd 166.05324. Found: 166.05330
str1

Scalable Photocatalytic Oxidation of Methionine under Continuous-Flow Conditions

Center for Integrated Technology and Organic Synthesis, Department of Chemistry, Nanomaterials, Catalysis & Electrochemistry - NCE, Department of Chemical Engineering, Biophotonics, Department of Physics, University of Liège, B-4000 Liège (Sart Tilman), Belgium
§ Corning Reactor Technologies, Corning SAS, 7 bis Avenue de Valvins, CS 70156 Samois sur Seine, 77215 Avon Cedex, France
Org. Process Res. Dev., Article ASAP
DOI: 10.1021/acs.oprd.7b00212
 
Highly efficient and chemoselective singlet oxygen oxidation of unprotected methionine was performed in water using a continuous mesofluidic reactor. Sustainable process engineering and conditions were combined to maximize process efficiency and atom economy, with virtually no waste generation and safe operating conditions. Three water-soluble metal-free photosensitizers [Rose Bengal, Methylene Blue, and tetrakis(4-carboxyphenyl)porphyrin] were assessed. The best results were obtained with Rose Bengal (0.1 mol %) at room temperature under white light irradiation and a slight excess of oxygen. Process and reaction parameters were monitored in real-time with in-line NMR. Other classical organic substrates (α-terpinene and citronellol) were oxidized under similar conditions with excellent performances.
Abstract Image

Ascaridole

str1
Ascaridole (2b). 1H NMR (CD3OD, 400 MHz): δ = 6.5 (dd, 2H), 1.97 (d, 1H), 1.88 (m, 1H), 1.56 (d, 1H), 1.34 (s, 3H), 1.00 (m, 6H). NMR data matched those reported in the literature.1,2 ESI HRMS m/z C10H16O2Na [M+Na]+ : calcd 191.10425. Found: 191.10418.
//////////http://pubs.acs.org/doi/suppl/10.1021/acs.oprd.7b00212/suppl_file/op7b00212_si_001.pdf
Ascaridole δ: 1.03 (d, J = 6.9, H9, H10), 1.39 (s, H7), 1.52 (d, J = 9.0, H5), 1.91 (sept, J = 6.9, H8), 2.07 (d, J = 9.0, H6), 6.43 (d, J = 8.7, H3), 6.51 (d, J = 8.7, H2). http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-695X2016000100056

Friday 14 July 2017

Catalytic carbonyl hydrosilylations via a titanocene borohydride-PMHS reagent system

DOI: 10.1039/C7CY01088E, Paper
Godfred D. Fianu, Kyle C. Schipper, Robert A. Flowers II
Catalytic amounts of titanocene(III) borohydride, generated under mild conditions from commercially available titanocene dichloride, in concert with a stoichiometric hydride source is shown to effectively reduce aldehydes and ketones to their respective alcohols in aprotic media.
  • Catalysis Science & Technology

Catalytic carbonyl hydrosilylations viaa titanocene borohydride–PMHS reagent system

Abstract

Reduction of a wide range of aldehydes and ketones with catalytic amounts of titanocene borohydride in concert with a stoichiometric poly(methylhydrosiloxane) (PMHS) reductant is reported. Preliminary mechanistic studies demonstrate that the reaction is mediated by a reactive titanocene(III) complex, whose oxidation state remains constant throughout the reaction.
Godfred Fianu

Godfred Fianu

Robert A Flowers

Robert A Flowers

Danser Distinguished Faculty Chair in Chemistry and Deputy Provost for Faculty Affairs
Lehigh University
Bethlehem, United States
Phenyl methanol (2-c)
Phenyl methanol (2-c) was prepared from benzaldehyde (1-c) by the procedure outlined
in GP1. NMR analysis showed 100% conversion in 1 hour. 86% isolated yield of alcohol
product was obtained after complete workup.
1H NMR (400 MHz, CDCl3) δ 7.37 – 7.26 (m,5H), 4.59 (s, 2H), 2.99 (s, 1H).
13C NMR (101 MHz, CDCl3) δ 140.92, 128.56, 127.60, 127.07,77.52, 77.20, 76.88, 65.04.
STR1 STR2
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Thursday 13 July 2017

2,2,5,5-Tetramethyltetrahydrofuran (TMTHF): a non-polar, non-peroxide forming ether replacement for hazardous hydrocarbon solvents



2,2,5,5-Tetramethyltetrahydrofuran (TMTHF): a non-polar, non-peroxide forming ether replacement for hazardous hydrocarbon solvents
Green Chem., 2017, Advance Article
DOI: 10.1039/C7GC01392B, Paper
Fergal Byrne, Bart Forier, Greet Bossaert, Charly Hoebers, Thomas J. Farmer, James H. Clark, Andrew J. Hunt
An inherently non-peroxide forming ether solvent, 2,2,5,5-tetramethyltetrahydrofuran (2,2,5,5-tetramethyloxolane), has been synthesized from readily available and potentially renewable feedstocks, and its solvation properties have been tested

2,2,5,5-Tetramethyltetrahydrofuran (TMTHF): a non-polar, non-peroxide forming ether replacement for hazardous hydrocarbon solvents

 

http://pubs.rsc.org/en/Content/ArticleLanding/2017/GC/C7GC01392B?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+rss%2FGC+%28RSC+-+Green+Chem.+latest+articles%29#!divAbstract

Abstract

An inherently non-peroxide forming ether solvent, 2,2,5,5-tetramethyltetrahydrofuran (2,2,5,5-tetramethyloxolane), has been synthesized from readily available and potentially renewable feedstocks, and its solvation properties have been tested. Unlike traditional ethers, its absence of a proton at the alpha-position to the oxygen of the ether eliminates the potential to form hazardous peroxides. Additionally, this unusual structure leads to lower basicity compared with many traditional ethers, due to the concealment of the ethereal oxygen by four bulky methyl groups at the alpha-position. As such, this molecule exhibits similar solvent properties to common hydrocarbon solvents, particularly toluene. Its solvent properties have been proved by testing its performance in Fischer esterification, amidation and Grignard reactions. TMTHF's differences from traditional ethers is further demonstrated by its ability to produce high molecular weight radical-initiated polymers for use as pressure-sensitive adhesives.
STR1
[TMTHF].
1H NMR (400 MHz, CDCl3): δ 1.81 (s, 4H), 1.21 (s, 12H);
13C NMR (400 MHz, CDCl3): δ 29.75, 38.75, 80.75;
IR 2968, 2930, 2968, 1458, 1377, 1366, 1310, 1265, 1205, 1144, 991, 984, 885, 849, 767 cm−1;
m/z (%): (ESI–MS) 128 (40) [M+ ]
STR1

Fergal Byrne

Fergal Byrne

PHD Researcher at Green Chemistry Centre of Excellence

University of York

York, United Kingdom

University of York
Green Chemistry Centre of Excellence, University of York, York YO10 5DD, UK 

Andrew Hunt

Andrew Hunt

Catalysis, Environmental Chemistry, Green Chemistry

PhD.
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NMR predict
[TMTHF].
1H NMR (400 MHz, CDCl3): δ 1.81 (s, 4H), 1.21 (s, 12H);
STR1 STR2
13C NMR (400 MHz, CDCl3): δ 29.75, 38.75, 80.75;

Wednesday 12 July 2017

Benzo[d]oxazol-2(3H)-one

IH NMR ABOVE
13C NMR BELOW
Benzo[d]oxazol-2(3H)-one (2a)
pale yellow crystals; mp 140.5–141.5 °C (lit.(6a) 134–136 °C);
 
1H NMR (300 MHz, CDCl3) δ 9.90 (s, 1H), 7.26–7.09 (m, 4H);
 
13C NMR (75 MHz, CDCl3) δ 156.3, 143.9, 129.4, 124.2, 122.8, 110.3, 110.2.
 
NMR PREDICT
 
1H NMR PREDICT
 
13C NMR PREDICT
 
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http://pubs.acs.org/doi/full/10.1021/acs.oprd.7b00217

Monday 10 July 2017

NaBH4, twin screw technology (i.e., granulator, melt extruder, etc.) to yield the desired product in a continuous manner


Abstract Image
In this work the application of green chemistry principles such as process intensification and the replacement of reagents and solvents to more benign alternatives were coupled with the advantages of continuous manufacturing. The reduction of lipophilic aromatic aldehydes using an aqueous alkaline solution of NaBH4 was achieved by means of mechanical shearing and kneading provided by a custom-made batch reactor at the lab scale and a twin screw extruder at the kilo scale. The process was run continuously for 17 min to yield 1.41 kg of product (89% purity). The benefits of running the process in a continuous manner instead a conventional fed-batch mode were discussed in terms of both environmental and economic factors.

Screwing NaBH4 through a Barrel without a Bang: A Kneaded Alternative to Fed-Batch Carbonyl Reductions

Institute of Chemical and Engineering Sciences, 1 Pesek Road, 627833, Jurong Island, Singapore
Org. Process Res. Dev., Article ASAP
DOI: 10.1021/acs.oprd.7b00107
 
 
 
Image result for Valerio Isoni
Institute of Chemical & Engineering Sciences (ICES)
Institute of Chemical and Engineering Sciences, 1 Pesek Road, 627833, Jurong Island, Singapore
The chemical industry has been a major part of the Singapore economy for many years, based on a strong foundation as a major oil refining centre with a long history, and strategically placed at the heart of the Asia - Pacific region. In recent years the pharmaceuticals industry has also seen major growth, so that chemistry and chemical engineering science now make a very significant contribution to Singapore's economy.
In order to strengthen this position and to foster future development to grow from dependence solely on manufacturing to secure a more knowledge dependant, high tech research and development based business environment, Agency for Science, Technology and Research (A*STAR) and Economic Development Board (EDB) looked at how to bolster the local science and technology base. As a result, the Institute of Chemical and Engineering Sciences (ICES) came into being, to provide highly trained R&D manpower, to establish a strong science base and to develop technology and infrastructure to support future growth.
Starting from a small centre in the National University of Singapore (NUS), ICES was established as an autonomous national research institute under A*STAR on October 1st 2002. Since that time, we have grown rapidly. We have established world leading laboratories, pilot facilities, and the necessary infrastructure to carry out a world class research programme in chemistry and chemical engineering sciences. We have the capability to cover the range of activities from exploratory research to process development, optimisation and problem solving. We can go from very small lab scale right to kg and pilot scale in one organisation, with all of the necessary skills directly at hand and integrated into a project oriented environment.
 
 
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Thursday 6 July 2017

Increasing global access to the high-volume HIV drug nevirapine through process intensification




 


Increasing global access to the high-volume HIV drug nevirapine through process intensification
Green Chem., 2017, 19,2986-2991
DOI: 10.1039/C7GC00937B, Paper
Jenson Verghese, Caleb J. Kong, Daniel Rivalti, Eric C. Yu, Rudy Krack, Jesus Alcazar, Julie B. Manley, D. Tyler McQuade, Saeed Ahmad, Katherine Belecki, B. Frank Gupton
Fundamental elements of process intensification were applied to generate efficient batch and continuous syntheses of the high-volume HIV drug nevirapine.

Green Chemistry

Increasing global access to the high-volume HIV drug nevirapine through process intensification

 

Abstract

Access to affordable medications continues to be one of the most pressing issues for the treatment of disease in developing countries. For many drugs, synthesis of the active pharmaceutical ingredient (API) represents the most financially important and technically demanding element of pharmaceutical operations. Furthermore, the environmental impact of API processing has been well documented and is an area of continuing interest in green chemical operations. To improve drug access and affordability, we have developed a series of core principles that can be applied to a specific API, yielding dramatic improvements in chemical efficiency. We applied these principles to nevirapine, the first non-nucleoside reverse transcriptase inhibitor used in the treatment of HIV. The resulting ultra-efficient (91% isolated yield) and highly-consolidated (4 unit operations) route has been successfully developed and implemented through partnerships with philanthropic entities, increasing access to this essential medication. We anticipate an even broader global health impact when applying this model to other active ingredients.
Preparation of Nevirapine (1).

Preparation of CYCLOR (7), Step 1A: To a solution of CAPIC (2, 15 g, 105 mmole, 1.0 equiv) in diglyme (75 mL) in a 500 mL 3-neck round-bottom flask fitted with overhead stirrer, thermocouple, and addition funnel was added NaH (7.56g, 189 mmole, 1.8 equiv). The reaction mixture was stirred at room temperature for 30 minutes and gradual evolution of H2 gas was observed. The temperature of the reaction mixture was slowly increased to 60 °C (10 °C/hr increments). A preheated (55 °C) solution of MeCAN (5, 21.19 g, 192.2 mmol, 1.05 equiv) in diglyme (22.5 mL) was added over a period of an hour to the reaction mixture kept at 60 °C. The reaction mixture was allowed to stir at 60 °C for 2 hours. If desired, 7 may be isolated at this stage. The reaction mixture is cooled to 0 – 10 °C and the pH is adjusted to pH 7-8 using glacial acetic acid and stirred for an hour. The precipitate is collected by vacuum filtration and dried under vacuum to a constant weight to afford CYCLOR (7) (29.89g, 94%).
1H NMR (300MHz, CHLOROFORM-d)  = 8.44 (dd, J = 1.8, 5.3 Hz, 1 H), 8.21 (d, J = 4.7 Hz, 1 H), 8.15 (br. s., 1 H), 7.87 (dd, J = 2.1, 7.9 Hz, 1 H), 7.54 (s, 1 H), 7.20 (d, J = 5.3 Hz, 1 H), 6.66 (dd, J = 4.7, 7.6 Hz, 1 H), 2.95 - 2.84 (m, 1 H), 2.35 (s, 3 H), 0.91 - 0.77 (m, 2 H), 0.62 - 0.47 (m, 2 H).
13C NMR (75MHz, CHLOROFORM-d)  = 166.8, 159.2, 153.2, 148.3, 146.9, 136.0, 129.9, 125.1, 111.1, 108.4, 77.4, 76.6, 23.8, 18.8, 7.0.
HRMS (ESI) C15H15ClN4O m/z [M+H] + found 303.0998, expected 303.1012.
Preparation of nevirapine (1), Step 1B: In a 150 mL, 3 neck flask, fitted with overhead stirrer, thermocouple and addition funnel, a suspension of NaH (7.14 g, 178.5 mmol, and 1.7 equiv) in diglyme (22.5 ml) was heated to 105 °C and crude CYCLOR (7) reaction mixture from Step 1 (preheated to 80 °C) was added over a period of 30 minutes while maintaining the reaction mixture at 115 °C. The reaction mixture was stirred for 2 hours at 117 °C for ~2 hours then cooled to room temperature. Water (30 mL) was added to quench the excess sodium hydride and the reaction was concentrated in vacuo to remove 60 mL of diglyme. To the resulting suspension was added water (125 mL), cyclohexane (50 mL) and ethanol (15 mL). The pH of the mixture was adjusted to pH 7 using glacial acetic acid (19.5 g, 3.09 mmol) at which precipitate formed. After stirring for 1 hour at 0 °C, the precipitate was collected via vacuum filtration and the filter cake was washed with ethanol: water (1:1 v/v) (2 x 20 mL). The solid was dried between 90-110°C under vacuum to provide nevirapine (25.4 g, 91% over two steps).
1H NMR (400MHz, CDCl3)  = 8.55 (dd, J = 2.0, 4.8 Hz, 1 H), 8.17 (d, J = 5.0 Hz, 1 H), 8.13 (dd, J = 2.0, 7.8 Hz, 1 H), 7.61 (s, 1 H), 7.08 (dd, J = 4.8, 7.8 Hz, 1 H), 6.95 (dd, J = 0.6, 4.9 Hz, 1 H), 3.79 (tt, J = 3.6, 6.8 Hz, 1 H), 2.37 (s, 3 H), 1.07-0.93 (m, 2 H), 0.59-0.50 (m, 1 H), 0.50-0.41 (m, 1 H).
13C NMR (101MHz, CDCl3)  = 168.4, 160.5, 153.9, 152.1, 144.3, 140.3, 138.8, 124.8, 121.9, 120.1, 118.9, 29.6, 17.6, 9.1, 8.8.
HRMS (ESI) C15H14N4O m/z [M+H] + found 267.1239, expected 267.1245.
Purification of nevirapine. To a cooled (0 °C) suspension of nevirapine (10g, 375.5 mmole) in water (43 ml) was added a 10 M solution of HCl (11.6 ml, 117.5 mmole) dropwise. The solution was allowed to stir for 30 minutes and activated carbon (0.3g) was added. After stirring for 30 minutes, the solution was filtered over Celite. The filtrate was transferred to flask and cooled to 0 °C. A 50% solution of NaOH was added dropwise until a pH of 7 is reached. A white precipitate appeared and the solution was stirred for 30 minutes and filtered. The solid was washed with water (3 x 10ml). The wet cake was dried between 90-110°C under vacuum to a constant weight to provide nevirapine (9.6 g, 96%).

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